Figure 3.

Association between pneumococcal polymerase chain reaction (PCR) load (log₁₀ copies/mL) in nasopharyngeal/oropharyngeal (NP/OP) and whole-blood (WB) specimens among cases without evidence of prior antibiotic exposure (Abx), by microbiologically confirmed pneumococcal pneumonia (MCPP) status. PCR load (density) in NP/OP specimens >6.9 log₁₀ copies/mL (horizontal line) demarks the optimal colonization load (density) threshold for discriminating MCPP cases from all controls [13]. The shaded area to the right denotes specimens with WB pneumococcal PCR load ≥2.2 log₁₀ copies/mL. MCPP was defined as pneumococcus isolated from culture of blood, lung aspirate, pleural fluid, PCR of lung aspirate or pleural fluid, or detection of Streptococcus pneumoniae antigen in pleural fluid on BinaxNOW. Nonconfirmed cases were defined as cases without isolation of bacteria from culture of blood, lung aspirate or pleural fluid, or PCR of lung aspirate or pleural fluid. Prior antibiotic exposure was defined as serum bioassay positive, antibiotic administration at the referral facility, or antibiotic administration prior to WB specimen collection at the study facility.